Sorry to hear - losses are no fun.
I just had similar experience. I bought an ATO secondhand early this year but still haven’t set it up
I still top off by hand twice a day. When central heating kicked in recently, evaporation increased & a couple of SPS had some STN. My salinity was too high & the swing was a bit wide. It was just a blip though & they are recovering fast. Maybe my poor coral are used to my antiquated system? Lol
I had a bit of that green stuff in previous tank & thought it was due to high nutrients?